La Jolla, CA – Salk Institute scientist Tony Hunter has been awarded the 2004 Louisa Gross Horwitz Prize, a leading national award for scientific achievement, for his pivotal discoveries about the chemical 'switch' that turns healthy cells into cancer cells.

Dr. Hunter, an American Cancer Society professor of molecular and cell biology at the Salk Institute for Biological Studies, La Jolla, shared the award with Anthony Pawson, of the Samuel Lunenfield Research Institute of Mount Sinai Hospital, Toronto.

"I feel very lucky to have been selected for this prestigious award and I'm honored to have received this recognition from my peers," said Dr. Hunter.

In 1979, Dr. Hunter discovered that a process called tyrosine phosphorylation was the chemical 'on-off' switch responsible for telling cells to multiply in an uncontrolled fashion, i.e., become cancerous. Discovery of this important signalling mechanism, which proved to be the underlying cause of many types of human cancer, revolutionized cancer medicine and, ultimately, led to the development of several innovative cancer therapies.

Phosphorylation – the addition of a tiny phosphate ion to a large protein molecule – is a common way in which the body turns on or off proteins such as enzymes. Thus, phosphorylation of proteins in cells, which is often triggered by external stimuli, acts as a signalling mechanism for cells to respond to their environment. Dr. Hunter discovered that phosphorylation of tyrosine, one of the 20 amino acids found in proteins, governed how cells multiply. The special proteins that attach phosphate to tyrosine are called tyrosine kinases.

Within months, the implications of Dr. Hunter's discovery for human disease had lit a fire under the scientific community and provided new directions for cancer research. The human genome project has now revealed that human DNA encodes at least 90 tyrosine kinases and over half of these have been implicated in triggering one or more types of cancer.

Three cancer drugs that inhibit tyrosine kinases are now available. The first, Gleevec®, was approved by the FDA in 2001 for a type of leukemia. Iressa® and Tarceva® have since been approved for treatment of lung cancer.

"It's very gratifying that we were able to do something that has actually led to therapies for human disease," said Dr. Hunter. "We hoped that when we were studying these model systems that we would understand something about human cancer, but there were no guarantees. It's obviously very exciting that our work did, in the end, lead to drugs that save lives."

The Louisa Gross Horwitz prize for biology or biochemistry is awarded by Columbia University and named after the mother of Columbia benefactor S. Gross Horwitz. Over half of the previous winners have gone on to win Nobel Prizes.

The Salk Institute for Biological Studies, located in La Jolla, Calif., is an independent nonprofit organization dedicated to fundamental discoveries in the life sciences, the improvement of human health and conditions, and the training of future generations of researchers. Jonas Salk, M.D., founded the institute in 1960 with a gift of land from the City of San Diego and the financial support of the March of Dimes.